Audio-video content, for example motion picture feature films, is often distributed in different encoding formats through various different distribution channels and on different digital media. Prior to distribution, video master data is maintained on the distribution side for creating compressed versions for distribution to end users. In the case of high-definition (HD) video data, master video data for large content files such as feature films may be large enough, for example about one terabyte (1000 gigabytes), to be subject to system storage or bandwidth limitations.
Therefore, “mezzanine compression” may be used to compress video master data. As used herein, “mezzanine compression” refers to a compression process used to create an intermediate electronic master (“eMaster”) file. The resulting electronic master file is considered intermediate because it is often not the final video compression that is applied to the video signal to be ultimately delivered to the consumer or customer, and is compressed less than end user files. As such, mezzanine compression is a mild compression that should not reduce the image quality of any of the downstream deliverables. For example, mezzanine compression ratios are typically in the range of about 3:1 to 15:1. This means, for example, instead of requiring 833 gigabytes to encode a 2-hour HD raw video master, an 2-hour HD eMaster using a 3:1 compression ratio requires 833/3=277 gigabytes, while a 2-hour HD eMaster using a 15:1 compression ratio requires 833/15=55 gigabytes. Mezzanine compression reduces storage requirements and also reduces the transfer bandwidth requirements of the eMaster since less data is transmitted over high-speed networking equipment.
Wavelet compression, for example compression according to the Joint Photographic Experts Group (“JPEG”) 2000 standard, may be suitable for mezzanine compression to produce eMaster files. However, the JPEG 2000 or similar wavelet compression methods may be subject to certain disadvantages when used for mezzanine compression, which demands a higher level of precision and accuracy than compression for end-use applications. For example, wavelet compression methods may be subject to ringing artifacts or other imprecision near luma or chroma limits of the image, which may appear as blurriness or discoloration in certain image areas.
Therefore, it would be desirable to provide a method or system for improving wavelet compression or other compression methods with similar disadvantages, that overcomes these and other limitations of the prior art.